Spark-plug.



w. n. HUNTER.

SPARK PLUG. APPLICATION FILED MAR. l?, 19H.

Patented Dec. 24, 1918.

WILLIAM B. HUNTER, 0F CHICAGO, ILLINOIS.

SPARK-PLUG'.

Specification of Letters Patent.

Patented Dee. 24, 1918.

Application tiled Hal-'ch 17, 1917. Serial No. 155,407.

To all 'whom it may concern:

Be it known that I, WILLIAM R. HUNTER, a citizen of the United States, residingat Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Spark-Plugs, of which the following is a speciiication. This invention relates to spark plugs .for internal combustion engines and has for its primary object the provision of a device of simple and relatively inexpensive construction embodying numerous advantageous features and designed particularly to permit relative changes of proportions between the shell and core resulting from the dilerent coefficients of expansion of the materia-ls from which these parts are constructed.'

A further object ofmy invention is the provision of a spark plug so constructed that particles of carbonl can not accumulate between the shell and the central electrode to short-circuit the plug.

Further objects and advantages of my inl vention will be apparent as it is better understood by refe-rence to the following specification when read in connection with the accompanying drawing illustrating the preferred embodiment thereof, in which- Figure 1 is a longitudinal section through a spark plug according to my invention; Fig. 2 is a plan view of the electrode end of the plug, and

F gs. 3 to 9, inclusive, are details in perspective ofthe various parts of the plug, s ome of the figures being in section to better illustrate the construction.

Referring to the drawing, 5 indicates a metal shell threaded at 6 in the usual man- 11er and provided with an internal flange 7. Mounted within the shell on opposite sides of the flange 7 are sections 8 and 9 of an insulating core, preferablyv of vitreous material. Washers 10 of asbestos or other suitable material are disposed -between the sides of the flange 7 and the contiguous ends of the sections 8 and 9. The section 9 is provided at its inner end with a recess 11 to receive the reduced portion 12 of the sec-- tion 8.

A central electrode 13, having a flattened end 14 and a flange 15, passes through the. sections 8 and 9y of the core and is threaded at its opposite end to receive the nuts 16 and Y 17. A split or spring washer 18 is disposed between the lower nut 16 and the section 9 of thecore. When the parts are in assembled of the ysections of the core and inasmuch as the core engages the shell only at the ange 7 and through the resilient washers 10 it is apparent that free longitudinal expansion of the sections of the core with reference to the shell is possible. The resiliency of the washers 10 and the spring washer 18 permits expansion of the sections 8.and 9 with respect to the electrode 13. The tendency of the vitreous insulating core to crack under the strains set up by the relative changes in proportions resulting from the different coefficients of expansion of the materials constituting the plug is entirely overcome by the above-described construction. As will be readily understood the shell and core are freeto expand andcontract with reference to each other while the parts are still maintained in rigid assembled relation as i`s essential to the continued successful operation of the device.

An electrode 19 is secured to one end of the shell 5 in coperative relation to the flattened end 14 of the electrode 13. The edge of the attened end 14 is disposed in parallel relation to the end of the electrode 19 so that when the device is in use a spark of considerable area will be produced.` 'To overcomethe usual tendency of spark plu s to become foul with carbon, which eventual y bridges the'space between the shell and centralelectrode and short-circuits the plug,

the section 8 is extended beyond the end of the shell 5 as indicated at 20 and a recess 21 is formed in the end of the section through which the electrode 13 extends. By this construction the central electrode is separated changes may be made in the form, construction and arrangement of the parts without departing from the s pirt and scope of the invention or sacrificing any of its matebear against said ange, said lower section being substantially equal in diameter to the internal diameter of said shell and having a sloping shoulder engaging said flange and a shallow central recess'of relatively large diameter in its lower end, a centralelectrode projecting through said recess and provided 15 With a flattened end, means on said electrode to hold said sections in assembled relation,y and an electrode on said shell co operating with the flattened end of said central electrode. v

- WILLIAM R. HUNTER. Witnesses WM. O. BELT, M'. A. KIDDI. 

